[libvirt] [PATCHv2] qemu: Avoid holding the driver lock in trivial snapshot API's

Monday, 24 September 2012

In most of the snapshot API's there's no need to hold the driver lock
the whole time.

This patch adds helper functions that get the domain object in functions
that don't require the driver lock and simplifies call paths from
snapshot-related API's.
---
Diff to v1:
- remove touching domain configuration locking to handle NULL gracefully and
apropriate tweaks not to break code

 src/qemu/qemu_driver.c | 267 +++++++++++++++----------------------------------
 1 file changed, 79 insertions(+), 188 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 6848924..af14197 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -187,6 +187,60 @@ struct qemuAutostartData {
     virConnectPtr conn;
 };

+
+/* Looks up the domain obj and unlocks the driver */
+static virDomainObjPtr
+qemuDomObjFromDomain(virDomainPtr domain)
+{
+    struct qemud_driver *driver = domain->conn->privateData;
+    virDomainObjPtr vm;
+    char uuidstr[VIR_UUID_STRING_BUFLEN];
+
+    qemuDriverLock(driver);
+    vm = virDomainFindByUUID(&driver->domains, domain->uuid);
+    qemuDriverUnlock(driver);
+    if (!vm) {
+        virUUIDFormat(domain->uuid, uuidstr);
+        virReportError(VIR_ERR_NO_DOMAIN,
+                       _("no domain with matching uuid '%s'"),
uuidstr);
+    }
+
+    return vm;
+}
+
+
+/* Looks up domain obj from snapshot and unlocks the driver */
+static virDomainObjPtr
+qemuDomObjFromSnapshot(virDomainSnapshotPtr snapshot)
+{
+    return qemuDomObjFromDomain(snapshot->domain);
+}
+
+
+/* Looks up snapshot obj from VM and name */
+static virDomainSnapshotObjPtr
+qemuSnapObjFromName(virDomainObjPtr vm,
+                    const char *name)
+{
+    virDomainSnapshotObjPtr snap = NULL;
+    snap = virDomainSnapshotFindByName(vm->snapshots, name);
+    if (!snap)
+        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
+                       _("no domain snapshot with matching name
'%s'"),
+                       name);
+
+    return snap;
+}
+
+
+/* Looks up snapshot obj from VM and snapshotPtr */
+static virDomainSnapshotObjPtr
+qemuSnapObjFromSnapshot(virDomainObjPtr vm,
+                        virDomainSnapshotPtr snapshot)
+{
+    return qemuSnapObjFromName(vm, snapshot->name);
+}
+
 static void
 qemuAutostartDomain(void *payload, const void *name ATTRIBUTE_UNUSED,
                     void *opaque)
@@ -11305,22 +11359,14 @@ static int qemuDomainSnapshotListNames(virDomainPtr domain, char
**names,
                                        int nameslen,
                                        unsigned int flags)
 {
-    struct qemud_driver *driver = domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     int n = -1;

     virCheckFlags(VIR_DOMAIN_SNAPSHOT_LIST_ROOTS |
                   VIR_DOMAIN_SNAPSHOT_FILTERS_ALL, -1);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromDomain(domain)))
         goto cleanup;
-    }

     n = virDomainSnapshotObjListGetNames(vm->snapshots, NULL, names, nameslen,
                                          flags);
@@ -11328,36 +11374,26 @@ static int qemuDomainSnapshotListNames(virDomainPtr domain, char
**names,
 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return n;
 }

 static int qemuDomainSnapshotNum(virDomainPtr domain,
                                  unsigned int flags)
 {
-    struct qemud_driver *driver = domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     int n = -1;

     virCheckFlags(VIR_DOMAIN_SNAPSHOT_LIST_ROOTS |
                   VIR_DOMAIN_SNAPSHOT_FILTERS_ALL, -1);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromDomain(domain)))
         goto cleanup;
-    }

     n = virDomainSnapshotObjListNum(vm->snapshots, NULL, flags);

 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return n;
 }

@@ -11365,29 +11401,20 @@ static int
 qemuDomainListAllSnapshots(virDomainPtr domain, virDomainSnapshotPtr **snaps,
                            unsigned int flags)
 {
-    struct qemud_driver *driver = domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     int n = -1;

     virCheckFlags(VIR_DOMAIN_SNAPSHOT_LIST_ROOTS |
                   VIR_DOMAIN_SNAPSHOT_FILTERS_ALL, -1);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromDomain(domain)))
         goto cleanup;
-    }

     n = virDomainListSnapshots(vm->snapshots, NULL, domain, snaps, flags);

 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return n;
 }

@@ -11397,7 +11424,6 @@ qemuDomainSnapshotListChildrenNames(virDomainSnapshotPtr
snapshot,
                                     int nameslen,
                                     unsigned int flags)
 {
-    struct qemud_driver *driver = snapshot->domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     virDomainSnapshotObjPtr snap = NULL;
     int n = -1;
@@ -11405,23 +11431,11 @@ qemuDomainSnapshotListChildrenNames(virDomainSnapshotPtr
snapshot,
     virCheckFlags(VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS |
                   VIR_DOMAIN_SNAPSHOT_FILTERS_ALL, -1);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, snapshot->domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(snapshot->domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromSnapshot(snapshot)))
         goto cleanup;
-    }

-    snap = virDomainSnapshotFindByName(vm->snapshots, snapshot->name);
-    if (!snap) {
-        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
-                       _("no domain snapshot with matching name
'%s'"),
-                       snapshot->name);
+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
         goto cleanup;
-    }

     n = virDomainSnapshotObjListGetNames(vm->snapshots, snap, names, nameslen,
                                          flags);
@@ -11429,7 +11443,6 @@ qemuDomainSnapshotListChildrenNames(virDomainSnapshotPtr
snapshot,
 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return n;
 }

@@ -11437,7 +11450,6 @@ static int
 qemuDomainSnapshotNumChildren(virDomainSnapshotPtr snapshot,
                               unsigned int flags)
 {
-    struct qemud_driver *driver = snapshot->domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     virDomainSnapshotObjPtr snap = NULL;
     int n = -1;
@@ -11445,30 +11457,17 @@ qemuDomainSnapshotNumChildren(virDomainSnapshotPtr snapshot,
     virCheckFlags(VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS |
                   VIR_DOMAIN_SNAPSHOT_FILTERS_ALL, -1);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, snapshot->domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(snapshot->domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromSnapshot(snapshot)))
         goto cleanup;
-    }

-    snap = virDomainSnapshotFindByName(vm->snapshots, snapshot->name);
-    if (!snap) {
-        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
-                       _("no domain snapshot with matching name
'%s'"),
-                       snapshot->name);
+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
         goto cleanup;
-    }

     n = virDomainSnapshotObjListNum(vm->snapshots, snap, flags);

 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return n;
 }

@@ -11477,7 +11476,6 @@ qemuDomainSnapshotListAllChildren(virDomainSnapshotPtr snapshot,
                                   virDomainSnapshotPtr **snaps,
                                   unsigned int flags)
 {
-    struct qemud_driver *driver = snapshot->domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     virDomainSnapshotObjPtr snap = NULL;
     int n = -1;
@@ -11485,23 +11483,11 @@ qemuDomainSnapshotListAllChildren(virDomainSnapshotPtr
snapshot,
     virCheckFlags(VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS |
                   VIR_DOMAIN_SNAPSHOT_FILTERS_ALL, -1);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, snapshot->domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(snapshot->domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromSnapshot(snapshot)))
         goto cleanup;
-    }

-    snap = virDomainSnapshotFindByName(vm->snapshots, snapshot->name);
-    if (!snap) {
-        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
-                       _("no domain snapshot with matching name
'%s'"),
-                       snapshot->name);
+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
         goto cleanup;
-    }

     n = virDomainListSnapshots(vm->snapshots, snap, snapshot->domain, snaps,
                                flags);
@@ -11509,7 +11495,6 @@ qemuDomainSnapshotListAllChildren(virDomainSnapshotPtr snapshot,
 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return n;
 }

@@ -11517,64 +11502,41 @@ static virDomainSnapshotPtr
qemuDomainSnapshotLookupByName(virDomainPtr domain,
                                                            const char *name,
                                                            unsigned int flags)
 {
-    struct qemud_driver *driver = domain->conn->privateData;
     virDomainObjPtr vm;
     virDomainSnapshotObjPtr snap = NULL;
     virDomainSnapshotPtr snapshot = NULL;

     virCheckFlags(0, NULL);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromDomain(domain)))
         goto cleanup;
-    }

-    snap = virDomainSnapshotFindByName(vm->snapshots, name);
-    if (!snap) {
-        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
-                       _("no snapshot with matching name '%s'"),
name);
+    if (!(snap = qemuSnapObjFromName(vm, name)))
         goto cleanup;
-    }

     snapshot = virGetDomainSnapshot(domain, snap->def->name);

 cleanup:
-    if (vm)
-        virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
+    virDomainObjUnlock(vm);
     return snapshot;
 }

 static int qemuDomainHasCurrentSnapshot(virDomainPtr domain,
                                         unsigned int flags)
 {
-    struct qemud_driver *driver = domain->conn->privateData;
     virDomainObjPtr vm;
     int ret = -1;

     virCheckFlags(0, -1);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromDomain(domain)))
         goto cleanup;
-    }

     ret = (vm->current_snapshot != NULL);

 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return ret;
 }

@@ -11582,30 +11544,17 @@ static virDomainSnapshotPtr
 qemuDomainSnapshotGetParent(virDomainSnapshotPtr snapshot,
                             unsigned int flags)
 {
-    struct qemud_driver *driver = snapshot->domain->conn->privateData;
     virDomainObjPtr vm;
     virDomainSnapshotObjPtr snap = NULL;
     virDomainSnapshotPtr parent = NULL;

     virCheckFlags(0, NULL);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, snapshot->domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(snapshot->domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromSnapshot(snapshot)))
         goto cleanup;
-    }

-    snap = virDomainSnapshotFindByName(vm->snapshots, snapshot->name);
-    if (!snap) {
-        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
-                       _("no domain snapshot with matching name
'%s'"),
-                       snapshot->name);
+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
         goto cleanup;
-    }

     if (!snap->def->parent) {
         virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
@@ -11619,28 +11568,19 @@ qemuDomainSnapshotGetParent(virDomainSnapshotPtr snapshot,
 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return parent;
 }

 static virDomainSnapshotPtr qemuDomainSnapshotCurrent(virDomainPtr domain,
                                                       unsigned int flags)
 {
-    struct qemud_driver *driver = domain->conn->privateData;
     virDomainObjPtr vm;
     virDomainSnapshotPtr snapshot = NULL;

     virCheckFlags(0, NULL);

-    qemuDriverLock(driver);
-    vm = virDomainFindByUUID(&driver->domains, domain->uuid);
-    if (!vm) {
-        char uuidstr[VIR_UUID_STRING_BUFLEN];
-        virUUIDFormat(domain->uuid, uuidstr);
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromDomain(domain)))
         goto cleanup;
-    }

     if (!vm->current_snapshot) {
         virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT, "%s",
@@ -11653,14 +11593,12 @@ static virDomainSnapshotPtr
qemuDomainSnapshotCurrent(virDomainPtr domain,
 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return snapshot;
 }

 static char *qemuDomainSnapshotGetXMLDesc(virDomainSnapshotPtr snapshot,
                                           unsigned int flags)
 {
-    struct qemud_driver *driver = snapshot->domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     char *xml = NULL;
     virDomainSnapshotObjPtr snap = NULL;
@@ -11668,29 +11606,19 @@ static char *qemuDomainSnapshotGetXMLDesc(virDomainSnapshotPtr
snapshot,

     virCheckFlags(VIR_DOMAIN_XML_SECURE, NULL);

-    qemuDriverLock(driver);
-    virUUIDFormat(snapshot->domain->uuid, uuidstr);
-    vm = virDomainFindByUUID(&driver->domains, snapshot->domain->uuid);
-    if (!vm) {
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromSnapshot(snapshot)))
         goto cleanup;
-    }

-    snap = virDomainSnapshotFindByName(vm->snapshots, snapshot->name);
-    if (!snap) {
-        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
-                       _("no domain snapshot with matching name
'%s'"),
-                       snapshot->name);
+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
         goto cleanup;
-    }
+
+    virUUIDFormat(snapshot->domain->uuid, uuidstr);

     xml = virDomainSnapshotDefFormat(uuidstr, snap->def, flags, 0);

 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return xml;
 }

@@ -11698,30 +11626,17 @@ static int
 qemuDomainSnapshotIsCurrent(virDomainSnapshotPtr snapshot,
                             unsigned int flags)
 {
-    struct qemud_driver *driver = snapshot->domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     int ret = -1;
     virDomainSnapshotObjPtr snap = NULL;
-    char uuidstr[VIR_UUID_STRING_BUFLEN];

     virCheckFlags(0, -1);

-    qemuDriverLock(driver);
-    virUUIDFormat(snapshot->domain->uuid, uuidstr);
-    vm = virDomainFindByUUID(&driver->domains, snapshot->domain->uuid);
-    if (!vm) {
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromSnapshot(snapshot)))
         goto cleanup;
-    }

-    snap = virDomainSnapshotFindByName(vm->snapshots, snapshot->name);
-    if (!snap) {
-        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
-                       _("no domain snapshot with matching name
'%s'"),
-                        snapshot->name);
+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
         goto cleanup;
-    }

     ret = (vm->current_snapshot &&
            STREQ(snapshot->name, vm->current_snapshot->def->name));
@@ -11729,7 +11644,6 @@ qemuDomainSnapshotIsCurrent(virDomainSnapshotPtr snapshot,
 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return ret;
 }

@@ -11738,30 +11652,17 @@ static int
 qemuDomainSnapshotHasMetadata(virDomainSnapshotPtr snapshot,
                               unsigned int flags)
 {
-    struct qemud_driver *driver = snapshot->domain->conn->privateData;
     virDomainObjPtr vm = NULL;
     int ret = -1;
     virDomainSnapshotObjPtr snap = NULL;
-    char uuidstr[VIR_UUID_STRING_BUFLEN];

     virCheckFlags(0, -1);

-    qemuDriverLock(driver);
-    virUUIDFormat(snapshot->domain->uuid, uuidstr);
-    vm = virDomainFindByUUID(&driver->domains, snapshot->domain->uuid);
-    if (!vm) {
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromSnapshot(snapshot)))
         goto cleanup;
-    }

-    snap = virDomainSnapshotFindByName(vm->snapshots, snapshot->name);
-    if (!snap) {
-        virReportError(VIR_ERR_NO_DOMAIN_SNAPSHOT,
-                       _("no domain snapshot with matching name
'%s'"),
-                       snapshot->name);
+    if (!(snap = qemuSnapObjFromSnapshot(vm, snapshot)))
         goto cleanup;
-    }

     /* XXX Someday, we should recognize internal snapshots in qcow2
      * images that are not tied to a libvirt snapshot; if we ever do
@@ -11771,7 +11672,6 @@ qemuDomainSnapshotHasMetadata(virDomainSnapshotPtr snapshot,
 cleanup:
     if (vm)
         virDomainObjUnlock(vm);
-    qemuDriverUnlock(driver);
     return ret;
 }

@@ -12439,9 +12339,7 @@ qemuDomainOpenConsole(virDomainPtr dom,
                       virStreamPtr st,
                       unsigned int flags)
 {
-    struct qemud_driver *driver = dom->conn->privateData;
     virDomainObjPtr vm = NULL;
-    char uuidstr[VIR_UUID_STRING_BUFLEN];
     int ret = -1;
     int i;
     virDomainChrDefPtr chr = NULL;
@@ -12450,15 +12348,8 @@ qemuDomainOpenConsole(virDomainPtr dom,
     virCheckFlags(VIR_DOMAIN_CONSOLE_SAFE |
                   VIR_DOMAIN_CONSOLE_FORCE, -1);

-    qemuDriverLock(driver);
-    virUUIDFormat(dom->uuid, uuidstr);
-    vm = virDomainFindByUUID(&driver->domains, dom->uuid);
-    qemuDriverUnlock(driver);
-    if (!vm) {
-        virReportError(VIR_ERR_NO_DOMAIN,
-                       _("no domain with matching uuid '%s'"),
uuidstr);
+    if (!(vm = qemuDomObjFromDomain(dom)))
         goto cleanup;
-    }

     if (!virDomainObjIsActive(vm)) {
         virReportError(VIR_ERR_OPERATION_INVALID,
-- 
1.7.12


    

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[libvirt] [PATCHv2] qemu: Avoid holding the driver lock in trivial snapshot API's